JP7229456B2 - Sagger for firing lithium-ion battery electrode material and material for protective layer of the sagger - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sagger for firing a lithium ion battery electrode material and a protective layer for the sagger.

In recent years, with the development of technology, the performance of lithium ion secondary batteries can be improved, and they are widely applied in fields such as mobile phones, notebook computers, electric vehicles, and energy storage. A lithium ion secondary battery is mainly composed of a positive electrode material, a negative electrode material, an electrolyte and a separator. Among them, positive electrode materials include commercially available products such as lithium iron phosphate, lithium cobalt oxide, nickel cobalt lithium manganese oxide (ternary system), and nickel system. Materials such as graphite and lithium titanate are used as negative electrode materials. The performance of the cathode and anode materials determines the capacity, energy density and cycle characteristics of the battery. A brief description of the production process of the cathode material: the precursor of the cathode material, namely cobalt oxide or hydroxide (e.g. cobalt hydroxide, nickel cobalt manganese hydroxide, nickel cobalt hydroxide, nickel cobalt hydroxide aluminum, water Nickel manganese oxide, etc.), lithium source (such as lithium carbonate, lithium hydroxide, etc.) are mixed in a certain proportion, then put into a ceramic sagger in a certain amount, and then baked at a high temperature of 800-1100 ℃ for a long time. knot. When firing lithium cobalt oxide, lithium iron phosphate, and ternary cathode materials (nickel-cobalt-manganese molar ratios of 1:1:1, 5:2:3, 6:2:2), an excess of Lithium carbonate is used as the lithium source. Lithium carbonate becomes molten at high temperatures and easily permeates the surface of the sagger. It was confirmed that it adhered to the surface of the sag; ), or lithium nickel cobalt aluminum oxide, an excess of lithium hydroxide is usually used as the lithium source. Lithium hydroxide is mainly a dihydrate. lifespan is greatly shortened.

Patent Document 1 proposes the use of one or more of zirconia, alumina, magnesia, etc. as a coating material for the same purpose. Although the above materials are highly corrosion resistant, zirconia is expensive, alumina can react with lithium, magnesium-containing compounds such as magnesia have higher coefficients of thermal expansion, and none of the above materials Since it is a thermally expansive material, the coating tends to crack during repeated use, resulting in a decrease in adhesion. In addition, the life evaluation method described in Patent Document 1 is based on the case where it cannot be used. Since it is not clear whether the meaning of "unusable" is cracked, peeled off, or cracked, it is ambiguous to use it as a criterion.

Alumina was also mentioned in many documents as a material for forming corrosion resistant coatings. Alumina reacts with the lithium source lithium carbonate and lithium hydroxide at high temperature to form LiAlO ₂ . The formation of LiAlO ₂ suppresses further reaction between alumina and the raw material of the positive electrode material, thereby suppressing the corrosiveness derived from lithium and achieving the purpose of anti-corrosion. However, since the thermal expansion coefficient of _LiAlO2 is much higher than that of the sagger substrate, the coating using only alumina is prone to peel off from the sagger substrate during repeated heating and cooling of firing, and is resistant to heat. Corrosive effect is reduced.

In Patent Document 2, a secondary press method is used to press a corrosion-resistant coating layer on the surface of a sagger base material made of cordierite, mullite, etc., and the coating layer is mainly composed of zirconia and spodumene. do. These materials did not react with lithium carbonate as a raw material for sintering the positive electrode material, and could improve corrosion resistance to some extent and extend service life, but both zirconia and spodumene have positive coefficients of thermal expansion. material, and even if the blending ratio is adjusted, the difference in thermal expansion constant between the coating film and the base material is large. The protective layer is easily peeled off. Furthermore, the secondary pressing process used in Patent Document 2 is complicated, the pressed coating is uneven, and there is a risk of cracks due to a decrease in strength on the arc surfaces of the bottom and side surfaces of the sagger. .

CN103884190 publication

CN103311498 publication

In view of the above problems of the prior art, the present invention provides a sagger for firing a lithium ion battery electrode material having a protective layer (coating film) that has high corrosion resistance, high adhesion, and is difficult to peel off, and a protective layer that is difficult to peel off. intended to provide

A first invention provides a sagger for firing a lithium ion battery electrode material, comprising a sagger body (base material) and a protective layer covering at least the bottom of the inner surface of the sagger body, wherein the protective layer comprises: LiAlSiO ₄ having a negative coefficient of thermal expansion, and MgO, SnO ₂ , Al ₂ O ₃ , ZrO ₂ , ZrSiO ₄ , MgAl ₂ O ₄ , LiAlO ₂ , which are metal oxides and metallates having a positive coefficient of thermal expansion, A coating layer containing one or more substances selected from Li ₂ ZrO ₂ and LiAlSi ₂ O ₆ and having a controlled thermal expansion coefficient, wherein the thermal expansion coefficient of the protective layer and the sagger body is characterized by a ratio of thermal expansion coefficients of 1:1 to 2:1 .
A second invention is characterized in that the sagger body is made of cordierite, mullite or a mixture thereof. The sagger body can be made of a material containing cordierite, mullite, or a mixture thereof as a main component, but may be made of other materials.

Furthermore, in order for the sagger protective layer of the present invention to be effective, it should cover at least the bottom of the inner surface of the main body. preferable. Further, the inner surface of the sagger body of the present invention refers to the surface on which the raw material used for firing the electrode material is placed.

The sagger for firing a lithium ion battery electrode material of the present invention is used for firing an electrode material in a lithium ion secondary battery. The electrode materials include, but are not limited to: metal oxide lithium salts with a layered structure, such as lithium cobaltate, nickel-cobalt-manganese ternary materials, lithium-rich manganese-based materials, etc.; Those with an olivine structure, such as lithium iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, etc.; lithium manganate, nickel manganese binary materials, etc. with a spinel structure; titanium as a negative electrode material. Lithium oxide.

A third invention is a protective layer material for forming a protective layer on a sagger body, which is composed of LiAlSiO ₄ having a negative coefficient of thermal expansion and a metal oxide and a metalate having a positive coefficient of thermal expansion. _a mixture _{with one} or more _substances selected _from MgO , _SnO2 , _Al2O3 , ZrO2 _, ZrSiO4 , _{MgAl2O4 ,} LiAlO2 , _Li2ZrO2 , _LiAlSi2O6 The thermal expansion coefficient of the mixture is adjusted so that the ratio of the thermal expansion coefficient of the mixture and the thermal expansion coefficient of the sagger body is 1:1 to 2:1.

Since the sagger of the present invention employs the protective layer of the above components, when the raw material for the electrode material of the lithium battery is placed on the sagger and repeatedly subjected to high temperature sintering, the thermal expansion coefficient of the protective layer is Since the coefficient of thermal expansion is close to that of the main body, the protective layer has good adhesion to the surface of the sagger and is difficult to peel off. In general, if the thermal expansion coefficients of the coating film and the base material are not appropriate, the thin film will have unstable adhesiveness to the base material during repeated high-temperature firing, and will easily peel off. Either one or both of the metal oxide and the metal acid salt used as the protective layer component of the present invention have a positive thermal expansion coefficient, so that the thermal expansion coefficient is the same as LiAlSiO ₄ having a negative thermal expansion coefficient. Although the thermal expansion coefficient of the protective layer is still positive, it is possible to realize that the protective layer is difficult to peel off from the sagger body by approaching the positive thermal expansion coefficient of the sagger body.

In addition, since the sagger of the present invention is not easily corroded by the material placed on the sagger during firing, the service life is extended and the manufacturing cost of the electrode material can be reduced. That is, LiAlSiO ₄ in the protective layer of the present invention does not chemically react with the sagger body, nor does it chemically react with the electrode material (positive electrode material or negative electrode material) or the raw material of the electrode material, so that the material placed on the sagger body It was possible to suppress the reaction with and suppress the corrosion of the material to be placed on the sagger.

FIG. 1 is a sectional view showing an example of the sagger of the present invention. 2 is a partially enlarged view showing a cross section of the bottom of the sagger in FIG. 1. FIG. 2 is an XRD graph of the sagger protective layer for Example 1. FIG.

The present invention will be described in detail below.
The sagger 1 shown in FIG. 1 comprises a main body 2 and a protective layer 3 covering an inner surface 21 of the main body 2 . The raw material for the electrode material is placed on the inner surface 21 of the main body 2 when the sagger is produced. Moreover, in this embodiment, the protective layer 3 covers the entire inner surface 21 of the main body 2 including the bottom portion 211 and the wall surface 212 . From the partially enlarged view of the bottom portion 211 as in FIG. 2, the protective layer 3 is in intimate contact with the bottom portion 211 of the inner surface 21 .

In the manufacturing process of the lithium battery electrode material, the reason why the sagger 1 is gradually corroded is that lithium carbonate and lithium hydroxide, which are the firing raw materials of the positive electrode material and the negative electrode material, are oxidized with alumina, which is the main body material of the sagger 1. A chemical reaction with silicon occurs under high temperature conditions, and a new substance is generated. This product is different from the composition of the sagger 1 and has a large difference in thermal expansion coefficient. When the sagger 1 is used repeatedly, the product is gradually peeled off from the main body 2 of the sagger 1, so that the life of the sagger 1 is greatly reduced, and the product is a sintered battery material as a foreign matter. may get mixed in.

Therefore, the present inventors have found that by providing a protective layer 3 having a specific composition on the surface of the sagger 1, lithium carbonate and hydroxide used for firing a positive electrode material or a negative electrode material such as lithium titanate By blocking the contact of lithium or the like with the material of the sagger 1, the corrosion of the sagger 1 by lithium carbonate, lithium hydroxide, or the like can be effectively suppressed, and the service life of the sagger 1 can be extended.

Specifically, the LiAlSiO ₄ used in the protective layer 3 of the sagger 1 for firing a lithium ion battery electrode material of the present invention does not chemically react with the main body 2 of the sagger 1 and is an electrode material or an electrode material. Since it is a substance that does not chemically react with the raw material of , there is an effect that the sagger 1 is not easily corroded by the material placed on it during sintering. Furthermore, LiAlSiO ₄ is in a molten state at 1200° C. to 1300° C., and sufficiently permeates the surface layer of the sagger 1 through the pores of the surface layer of the sagger 1 . In addition, the protective layer 3 of the lithium ion battery electrode material firing sagger 1 of the present invention further extends the service life of the sagger 1 by further adding a filler having corrosion resistance in LiAlSiO ₄ . can do.

The inventors of the present invention have found that the components contained in the protective layer 3 of the sagger 1 need to consider not only their reactivity with respect to the positive electrode material and the negative electrode material, but also their thermal expansion coefficient. There is also a large difference in the coefficient of thermal expansion between the two, and the coating layer is easily peeled off from the surface of the sagger 1, and the effect of protecting the sagger 1 cannot be obtained. It will be mixed in the positive electrode material, and the positive electrode material will be contaminated.

Therefore, the protective layer 3 of the sagger 1 of the present invention uses LiAlSiO ₄ with a negative coefficient of thermal expansion (coefficient of thermal expansion) as a base material component, and a material with a positive coefficient of thermal expansion (coefficient of thermal expansion) as a filler, For example, one or more of MgO, SnO ₂ , Al ₂ O ₃ , ZrO ₂ , ZrSiO ₄ , MgAl ₂ O ₄ , LiAlO ₂ , Li ₂ ZrO ₂ and LiAlSi ₂ O ₆ are selected. , the thermal expansion coefficient of the protective layer 3 is adjusted so that the ratio of the thermal expansion coefficient of the protective layer 3 and the thermal expansion coefficient of the main body 2 of the sagger 1 is 1:1-2:1. improves adhesion to the sagger 1 and becomes difficult to peel off from the sagger 1.

The coefficient of thermal expansion of the protective layer 3 of the present invention is calculated as follows: the coefficient of thermal expansion of the base material component is A, the mass % in the protective layer 3 is x%, and the density is ρ _A the filler has a coefficient of thermal expansion of B, a mass percentage of y% in the protective layer 3, and a density of _ρB .

When only one type of filler is used, the coefficient of thermal expansion of the protective layer 3 of the present invention is calculated based on the following formula (1).

When two or more fillers are used (n≧2), the thermal expansion coefficient of the protective layer of the invention is calculated based on the following formula (2).

Table 1 shows physical properties such as thermal expansion coefficients and densities of the materials used in the present invention.

A sagger 1 for firing a lithium ion battery electrode material of the present invention comprises a body 2 and a protective layer 3, the body 2 of the sagger 1 is mainly composed of cordierite, mullite, or a mixture thereof, and The protective layer 3 is applied to the surface of the body 2 of the sagger 1 that contacts the electrode material. For the body 2 of the sagger 1, a commercially available one can be used. For example, mullite or mullite and cordierite are mixed by adding an appropriate amount of binder and water, and the resulting wet powder is added to a mold and press-molded. After being dehydrated, it is dried and baked at a high temperature.

The sagger 1 for sintering a lithium ion battery electrode material of the present invention can be produced by the following method, which comprises (1) the step of sintering the sagger 1 body 2 from cordierite, mullite, or a mixture thereof. and (2) forming the protective layer 3 by coating the surface of the sagger 1 body 2 in contact with the electrode material.
Step (1) can be performed based on various known methods for manufacturing the sagger 1 main body 2 .
_{As the} step (2), _currently known _coating methods _{can be} used. At least one selected from MgAl ₂ O ₄ , LiAlO ₂ , Li ₂ ZrO ₂ , LiAlSi ₂ O ₆ ) is applied to the inner surface 21 in contact with the electrode material of the sagger 1 main body 2, and after drying A coating layer 3 is formed.

As the coating method, various known methods such as dip coating, spray coating, and brush coating can be used.

Examples of the present invention will be described below, but the present invention is not limited to these examples and can be modified as appropriate without departing from the gist of the present invention.

<Example 1>
85 g of LiAlO ₂ (manufactured by Wako Pure Chemical Industries, Ltd.) and 15 g of LiAlSiO ₄ (manufactured by MARUSU GLAZE Co., Ltd.) were weighed, placed in a 1 L ceramic pot, and 300 ml of zirconium beads and 300 ml of water were added. , The pot is closed, and after grinding for 5 hours at normal temperature with a rotation speed of 100 rpm, the zirconium beads are removed, and an appropriate amount of water is added to obtain a uniform suspension with a solid content of 30%.

The suspension obtained as described above was brushed onto a ceramic test piece of the same material as the lithium battery positive electrode material sagger 1 (thermal expansion coefficient 3.8×10 ⁻⁶ /K, area 80 cm ² , mullite). A protective layer 3 having a thickness of about 100 μm was formed on a cordierite mixture), dried in an oven at 100° C., placed in a firing furnace, and fired at 1300° C. for 20 hours. After cooling to room temperature, a portion of the protective layer 3 was scraped off and subjected to an XRD test. The results are shown in FIG. From FIG. 1 it can be seen that LiAlO ₂ and LiAlSiO ₄ are distributed in the protective layer 3 with no significant change in structure. Also, the adhesion of the protective layer 3 was evaluated by visual inspection based on the following criteria. Table 2 shows the results.

Adhesion effect of protective layer 3:
◯: Good adhesion and no cracks on the surface of the protective layer 3 ×: Cracks occurred on the surface of the protective layer 3 .

Example 2-5
The conditions shown in Table 2 were performed in the same manner as in Example 1, and the adhesion of the protective layer 3 was evaluated. Table 2 shows the results.

Comparative Example 1-5
The same operation as in Example 1 was performed under the conditions shown in Table 2, and the results of evaluating the adhesion of the protective layer 3 are shown in Table 2.

Furthermore, cobalt oxide (manufactured by Wako Pure Chemical Industries, Ltd.) and lithium carbonate (manufactured by SQM Co., Ltd.), which are raw materials of lithium cobalt oxide, were mixed, and the ceramic test with protective layer 3 prepared in Examples 1 to 5 was performed. It was placed on a piece and baked at 1030° C. for 10 hours to make the cathode material. After that, the fired lithium cobaltate powder was removed, and changes in the protective layer 3 after firing were observed. did not react with protective layer 3. On the other hand, after firing the ceramic test piece without the protective layer 3 in the same manner, a reddish brown and difficult-to-remove adhesion layer was formed on the ceramic test piece, indicating that the above-mentioned positive electrode material reacted with the ceramic test piece. rice field.

Example 6
Lithium carbonate powder and cobalt oxide powder were mixed at high speed at a Li/Co molar ratio of 1.03. About 5 kg of the resulting mixed powder was placed in a sagger 1 consisting of a mixture of mullite and cordierite, the inner surface 21 of which was coated with the protective layer 3 shown in Example 1. The material was sintered under the following conditions: heated to 1030° C. over 6 hours, held for 10 hours, and cooled to normal temperature for 4 hours after reaction. The sagger 1 was removed and the lithium cobaltate product was removed to observe discoloration and adhesion of the sagger 1 bottom 211 . Thereafter, sintering was repeated in the same manner, and changes in the sagger 1 were observed. The results are shown in Table 3 and evaluated as follows.
○: The lithium cobaltate product can be easily taken out, and there is no residue on the surface of the sagger 1 △: There is a residue on the surface of the sagger 1 -: Stop using ×: Damage to the sagger 1 there is

Comparative example 6
An experiment was conducted in the same manner as in Example 6 except that the protective layer 3 as in Example 1 was not provided, and changes in the sagger 1 were observed. The same evaluation as in Example 6 was performed, and the results are shown in Table 3.

In Comparative Example 6, the solid content remaining on the bottom of the inner surface of the sagger 1 adhered during the sixth sintering, and the bottom 211 of the inner surface 21 was partly peeled off. In addition, except for the blue color of cobalt remaining, a remarkable reddish brown discoloration was observed. adheres to the surface and is difficult to remove. If it is forcibly removed, part of the product produced by the reaction between the bottom material of the sagger 1 and lithium will be mixed into the lithium cobaltate product, increasing impurities. On the other hand, in Example 6, even after 10 firings, the lithium cobalt oxide product was easily taken out without not only blue cobalt residue but also remarkable peeling and cracking on the surface of the sagger 1. I was able to From the above results, by using the protective layer 3 of the present invention, the reaction of the positive electrode material with the sagger 1 during the sintering process can be effectively suppressed, and the life can be extended. It was expressed that the objective of reducing the manufacturing cost of the positive electrode material can be achieved.

As described above, in this embodiment, the entire inner surface consisting of the bottom and wall surfaces of the inner surface of the main body 2 is covered. It is within the scope of rights of the present invention.

1 sagger 2 body 21 inner surface 211 bottom 212 wall surface 3 protective layer

Claims (3)

a sagger body,
a protective layer covering at least the bottom of the inner surface of the sagger body;
In a sagger for firing a lithium ion battery electrode material comprising
The protective layer is
LiAlSiO ₄ with a negative coefficient of thermal expansion, and MgO, SnO ₂ , Al ₂ O ₃ , ZrO ₂ , ZrSiO ₄ , MgAl ₂ O ₄ , LiAlO ₂ , which are metal oxides or metallates with a positive coefficient of thermal expansion, A coating layer containing one or more substances selected from Li ₂ ZrO ₂ and LiAlSi ₂ O ₆ and having a controlled thermal expansion coefficient, wherein the thermal expansion coefficient of the protective layer and the sagger body A sagger for firing a lithium ion battery electrode material, characterized in that the ratio of thermal expansion coefficients of 1:1 to 2:1. 2. The saggar for firing lithium ion battery electrode material according to claim 1 , wherein said body is made of cordierite, mullite or a mixture thereof . A protective layer material for forming a protective layer on the sagger body,
LiAlSiO ₄ with a negative coefficient of thermal expansion ;
MgO, _SnO2 , Al2O3 _, ZrO2 , _ZrSiO4 , _{MgAl2O4 ,} LiAlO2 _{, Li2ZrO2} , _LiAlSi2O6 , which are _metal oxides _{or metallates} with positive _thermal expansion coefficients consisting of a mixture with one or more substances selected from
A lithium ion battery electrode material, wherein the thermal expansion coefficient of the mixture is adjusted so that the ratio of the thermal expansion coefficient of the mixture and the thermal expansion coefficient of the sagger body is 1:1 to 2:1. Material for the protective layer of firing saggers.

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